This invention relates to a plate-shaped heat exchanger generally made of plastic and having a plurality of longitudinally extending flow channels which are separated from one another by longitudinally extending webs. The channels guide a heat transferring fluid. The opposite ends of the flow channels merge into collecting conduits which contain fluid inlet and fluid outlet ports.
Plate-shaped heat exchangers are known which are formed of two plates connected with one another by means of an arbitrary number of parallel-extending webs. In this manner a plurality of parallel-oriented flow channels for the heat transferring fluid is provided.
For forming fluid inlet and fluid outlet openings, the plates of known plate-shaped heat exchangers of the above type may be connected to one another at the free ends of the flow channels. For this purpose, the transverse webs between the two plates may be cut to appropriate lengths or may be omitted and the ends of the two plates may be sealingly connected with one another by applying heat and pressure and/or by interposing an adhesive.
The known plate-shaped heat exchangers are disadvantageous in that in the zone of the intended inflow the heat transferring fluid passes relatively rapidly through the associated flow channels while the peripherally arranged flow channels are charged with the heat transferring fluid with a delay. Thus, a trailing of the fluid occurs in the peripheral channels which adversely affects a uniform heat transfer. This disadvantage is particularly pronounced in cases where the known plate-shaped heat exchangers are used in heating systems for floors, walls or ceilings.
In order to attempt to remedy the above disadvantage, it has been known to provide a distributor pipe into which the individual flow channels merge and which is arranged unilaterally or bilaterally over the entire width of the heat exchanger plate. The distributor pipe may have a central inlet and a central outlet which may be expedient in a construction in which the introduction of the heat transferring fluid occurs on one plate side and the withdrawal of the heat transferring fluid is effected on the other plate side. There are further structures conceivable in which the introduction and the removal of the fluid is effected only at one transversal side of the heat exchanger. In such cases the deflection of the fluid is effected within the heat exchanger at the transverse end remote from the location of the introduction of the fluid. For this purpose, the heat exchanger plate is provided, approximately centrally and in the longitudinal direction, with a blocking web which divides the unilaterally arranged distributor pipe into an inflow part and an outflow part. At the opposite end of the heat exchanger plate the web has a recessed end which permits a transition of the fluid from the inflow plate side to the return plate side.
In case of a known central inflow in the heat exchanger plate, the disadvantageous characteristics of leading flow in the flow channels charged more or less directly and the trailing flow in the peripheral channels also exist.
It has been attempted to eliminate the disadvantage of leading and trailing flows by designing the flow channels with different cross-sectional areas. This measure results in a certain reduction of the above-discussed non-uniformity of the flow characteristics in the individual flow channels but, on the other hand, creates problems as concerns the pressure-stresses on the heat exchanger plate. It has to be noted in this connection that the heat exchanger plate, if used in heating systems for floors has to take up significant weight-supporting loads without an appreciable reduction of the flow passage area of the individual flow channels. Such an undesired reduction, however, occurs precisely when, for example, the cross-sectional dimensions of the flow channels increase from the middle of the plate towards the periphery thereof, assuming a central charging of the heat exchanger plate. Such a plate would be in the peripheral zone less resistant against loads than in its central zone; such differences, however, cannot be permitted in heat exchangers for the intended application.